The macerator/pump for our holding tank has started to cause problems. To get it started I have to turn the shaft with a screw driver. Once it starts it seems to work fine until it's time to run it again. Is it worn out or is there a solution to fixing it without buying a new one!!!

Sounds like worn or stuck brushes, or an open winding on the rotor.you'll have to open it up to find out.
If you can buy a new one before you open up the old one, you can replace it if necessary.
If you can get the old one working, return the new one.